Telephone trunking system.



C. S. WINSTON.

TELEPHONE TRUNKING SYSTEM.

APPLICATION FILED DEC. 10, 1910.

Patented 001. 13, 1914.

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' CHARLES S. WINSTON, OF CHICAGO, ILLINOIS, ASSIGNOB TO KELLOGGSWITCHBOARD AND SUPPLY COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OFILLINOIS.

TELEPHONE TRUNKING SYSTEM.

Patented 0a. 13, 1914.

Applicationfiled December 10, 1910. Seriai N 0. 596,650.

. To all whom it may concern Trunking Systems, of which the-following isa SPGCIfiCatIOH.

.My invention relates to trunking cord c rcuits for telephone systems,and more particu'larly to such systems in which supervisory relays arecontrolled over the line conductors of connected'sub-stations. Incertain trunk systems in which supervisory relays are adapted-to beenergized upon response of the'called subscriber, and are connecteddirectly to the line conductors of a called telephone line, there is atendency for such relays to momentarily attract or kick up theirarmatures when a sub-station is called, dueto a discharge from the lineconductors -andbridgedcondensers, through such relays after eachapplication of'ringing current to theline. Especially in trunk circuits,where a relay is locked up responsive to ene-rgization of suchsupervisory relays, this kickor momentary attraction, causes a premature..-spec ification and in the appended claims.

Referring to the accompanying drawing, the system there illustratedincludes two substations, C and D', which terminate in line -circuits atdifi'erent exchanges. The

. cord, circuit A which is in the same 'eX- changezwith the line circuitof sub-station ,ClQ-isawell known four-relay cord cir-v cuit-adapted forconnecting to the lines ter' minating in its exchange. The trunk circuitoi which the outgoing end is located in'thesame exchange; with the lineof substation is connected to the spring jack 14 inthe exchange ofsub-station C by means of the heavily'marked conductors 15 Thesub-station 5 is connected to its exchange by means of line conductors 1and 2 which terminate at contacts of cutoff relay CO. The line relay LRis associated with ,the line of sub-station C- and is adapted uponenergization to display the line lamp 3. The multiple. jacks 4,iii-practice, would appear indifferent positions of the switchboard andare adapted to be connected to by the answering plug 5 of cord circuitA. The said cord circuit A also includes a calling plug 6 which isadapted-for connection to spring jacks of other telephone lines in thesame exchange, or spring jacks leading to trunk circuits as B in distantexchanges. The'said cord circuit N -also includesha tip, answeringsupervisory relay 7, and a sleeve answering supervisory relay 8,

which through theircoiiperation control the answering supervisory lamp.9. The calling supervisory relays 10 and 11, are adapted by theircooperation to control the calling supervisory lamp 12. The test relay'13 is connected through normal contacts of relay 11 to the tip contactof the calling plug 6. The operators telephone 0 is adapted for use withcord circuit A and other such circuits which may be used by the sameoperator: The order wire switch contacts OW are adapted to connect theoperators telephone 0 with the operators telephone, 0 in a distantexchange.

3 Spring jack 14 is connected to trunk circuit B at a distant exchangeby means of the heavily marked conductors 1-5 and 16 which terminate atthe incoming end of the said trunkcircuit B in the windings 17 and 18 ofrepeating coil 19, the said windings having condenser 20 interposedbetween their terminais. The other windings 21 and 22 of the saidrepeating coil 19, have the condenser 23 interposed between the innerterminals, the said windings being connected by means of the heavilymarked conductors to the plug 24. The; said trunk circuit B alsoincludes a sleeve supervisory relay SR --and a tip supervisory relayTR,a supervi= sory signal lamp 25 and a ringing lamp 26. Normally in bridgeof-the incoming end of trunk circuit B is the high resistance, slowacting relay 27.

The-relay 28. which is of comparatively low resistance to relay 27 isadapted upon operation of tip relay TR, to be connected in bridge of theincoming end of trunk circuit B in place of the high resistance relay27.

The signal controlling relay SC is adapted, upon response of i calledsubscriber, to efface-ringing lamp 26 and is locked in its energizedposition to revent a further display of said lamp until t e plug 24 hasbeen withdrawn from a connected spring jack. The

ringing key of the. trunk circuit B includes four sets of springs 29,each one being adapted to connect a diiierent frequency of ringingcurrent to the terminals of a called party line, for the purpose ofringing selectively any one of the sub-stations connected thereto. Theplungers which operate the springs29, are soarranged that the contactsprings 30 and the selected springs 29, are closed only when any of theringing plungers are in a fully depressed position, the said springs30being common to the actuating plungers for the four contact sets 29. Theringing relay31 is adapted to be energized when the contact springs 30are closed, so as to connect ringing current to the terminals of thecalled line and open the talking conductors of the trunk circuit.

The telephone line of sub-station D isequipped similar to thatofsub-station C except that it has four telephones, one beingconnectedto each of the terminals D, D and D Having described in generalthe apparatus used in the system illustrated, the op-' eration of thesaid system in connecting two subscribers in different exchanges willnow be described. Assuming subscriber at substation C. desiresconnection with a subscriber at sub-station D he would remove receiver32 from its switch hook, thereby establishing a circuit through linerelay LR from ground, normal contact 33, line conductors and sub-stationC normal contact 34, the winding of relay LR to battery, energizing saidrelay LR and lighting line lamp 3. The operatorin response to saidsignal inserts: answering plug 5 into a jack '4, thereby establishing'anenergizing circuit for relays 8 and CO traced from battery through thewinding of relay 8, the sleeve contacts of plug 5 and jack 4, andthrough the Winding of relay CO to ground. The said relays are thereuponenergized, the cutoff relay CO interrupting the circuit through linerelay LR, thereby eiiacing line lamp 3. A circuit for relay 7 is alsoestablished from battery over the previously described path to alternatecontact 34 of'relay CO, then over the line conductors and throughsub-station C, tip contact of jack 4 and plug 5 and through the windingof re lay 7 to ground, energizing the said relay. The operator thenactuates listening key 35 toascertain the wants of the callingsubscriber.

Assuming, as previously stated, that the calling subscriber atsub-station O desires connection with sub-station D which is in adistant exchange, the operator presses the order wire button OW leadingto the exchange in which the line of sub-station D terminatesandinquires of the distant operator which trunk is to be used for theconnection. The operator at the first exchange new inserts the callingplug 6 into a jack 14 of the assigned trunk circuit. Responsive .to thesaid connection a circuit for relay 11 is' established from batterythrough the winding of said relay 11, tip contact of plug 6 and jack 14,through impedance coil 37 to ground, energizing the said relay 11 andlighting the supervisory lamp 12 over a cir cuit established fromground, through the normal contact of relay 10, alternate contact 38 ofrelay -11 and lamp 12 to battery. Responsive to the energizatlon ofrelayll the alternate contact 39 is closed, thereby establishing acircuit through relay 27 of trunk circuit B traced from ground throughrelay 10, over conductor 16 through winding of relay 27 and back throughconductor 15 and relay l1 to-battery, energizing relay 27. The saidrelay 27 being of a comparatively high resistance, sufficient currentdoes not flow through its winding to the jack ofcalled substation asyet, upon energization of relay 27, lamp 25 Will'light, indicating tothe trunk operator that the first operator has connected with the propertrunk, or if the trunk operator 'plugs into a jack 4!), and lamp 25lights, the trunk operator will know the first operator has not pluggedinto jack 14, due to relay 27 failing toenergize.

The operator at trunk-circuit B having ascertained from the operatoratcord circuit A the number of the called subscriber, now tests the jack40 of the called subscriberby touching the tip of the plug 24 to thesleeve of jack 40. If the called line is busy, the test relay 41 isenergized in a well known manner by battery flowing from the sleevecontact of jack 40, and the operator receives a click in her receiverdue to the closing of a circuit through the middle winding of inductioncoil 42. If the line of the called subscriber is idle there will be nopotential above ground on the sleeve contact of jack 40 and test relay41 Will therefore not energize, and the operator not receiving a busyclick inserts the plug 24 into a jack'4O of the called line. Responsiveto the said connection an energizingcircuit is established throughcutoff relay-CO and the supervisory relay SR, traced from ground throughthe winding of said relay CO, sleeve contacts of jack 40 and plug 24,conductor 43, through the winding of relay SE to battery.'l" Theenergization'of the relay CO removes the sub-station control of a linerelay LR and also establishes a con. tinuity of the talking conductorsof the' trunk circuit B to. the terminals of said sub-station D.Responsive to the energization of relay SE, a circuit through ringmglamp 26 is established from ground through alternate contact 44, normalcontact 45, through said lamp 26 to battery,

lighting the said lamp. The trunk operator now actuates a ringing buttonto connect the proper ringing generator to the line of the calledsubstation. The actuation of said key closes the proper ringing springs29 and the cont-act springs 30; and'responsive to the closing of contactsprings 30, a circuit through relay '31 is established, from groundthrough alternate contact 44, normal contact 45, contact 30 to windingof relay 31 to battery at alternate contact 47, energizing said relay 31and closing alternate contacts 48 and 49. A path for. ringing current 1sthereby established, from generator through the closed alternate contact29, alternate contact 49, tip contacts of plug 24 and jack 40,-alternate, contact 33 over the line conductors 1', 2, and through thecondenser and call bell of sub-station D, alternate contact 34, sleevecontacts of jack 40 and plug 24, through alternate contacts 48 andresistance 50 to ground. The operator actuates the selected key severaltimes to ring the bell of the substation D- and upon each restoration ofthe actuated key the contact 30 and contact- 29 are restored to normal.

Upon each actuation of the said ringing key, the line conductors andcondensers in bridge thereof are charged from the. applied ringingcurrent, and upon each restoration of the said ringing. key, contacts 30land 29 are opened and the said line conductor and condensers willdischarge to ground through the winding of the tip relay TR'causing atendency-of the said relay TR to kick up its armature, opening thecircuit through the slow relay 27 and establishing a circuit through therelay 28 through alternate contact 52. This momentary attrac-' tion ofthe armature of relay TB is not of suflic'ient duration to allow therelay 27 to.

release its armature, it being slow acting, so that even should relay 28be energized by current from cord circuit A, the relay 27 not havingreleased its armature, a premature energizing circuit forrelay SC is notclosed. It will thus be seen, that-due to the .circuit arrangement justdescribed the relay SC will not be energized to prematurely efi acc theringing lamp 26.

The trunk operatorhavin signaled the subscriber at sub-station D asdescribed,

upon response of the said subscriber by the removal of receiver 32 fromit's switch hook, a circuit for the tip relay TR is established, fromground through the winding of said relay TR, alternate contact 53 ofrelay SR, normal contact 49, tip contacts of plug 24 and jack 40, overthe line conductors and through the called substation, back throughsleeve contacts of the jack 4O "and-plug 24, conductor 43,'and thewindingsof relay SR to battery. Relay TB is thereupon energized,interrupting the circuit throughrelay 27, allowing said relay todeenergize, and establishing a circuit through the lower re- "sistancerelay 28, by the closing of alternate contact 52 of relay TR. Theclosing of this low resistance path through the winding of relay 28,allows relay 10 of the cord circuit A to energize, elfacing ,thesupervisory lamp l2 and notifyingthe operator of cord circuit A that thecalled subscriber ha responded.

Returning noW to relay 28, upon its said 'energization, a" circuitthrough the relay SC is established, from battery through normal contact47 of relay 27, alternate contact 55, through the Winding'of relay SC toound at alternatecontact44 of relay SR. Responsive to the energizationof relay SC the circuit through ringing lamp 26 is' interrupted atcontact 45, and the said lamp is in a conversational circuit traced overthe heavily marked conductors, talking current for the callingsubscriber being supplied through the relays 7 and 8 of cord circuit A,and talking current for the called subscriber being supplied through therelays TR and SR ofthe'trunk circuit B. While I have shown severalbatteries at each exchange, it is to be understood that they may be oneand the same, that is, each exchange to have but a single battery.

Afterthe subscribers have finished conversation they replace theirreceivers upon their respective switch hooks. The restoratlon of thecalling subscribers receiver, opens the circuit through relay 7 of thecord circuit A allowing the said relay to de energize and close acircuit through supervisory lamp 9.

Uponthe called subscriber replacing his receiver upon itssWitch-hook,the previously traced circuit throughrelays TR and SR is interrupted,allowing the said relay TR to deenergize, but the relay SR remainsenergized dueto thecircuit through the cutoff relay CO. Upondeenergization of tip rclay TR, the circuit through the low resistancerelay 28 is interrupted at contact 52, and a circuit through the highresistance re- .lay 27;is againestablished over the pre- A in responseto the signal received fromthe lighted lamps 9 and 12, withdraws theplugs 5 and 6 from their respective spring jacks, restoring theapparatusof cord circuit A to. normal and also restoring cutofi' relayC0 of the calling line. Upon Withing the low resistance path throughrelay 28.

drawal of plug 6 of cord circuit A from spring jack 14.,the circuitthrough relay 27 of trunk circuit B is interrupted and the said relay isdeenerg'ized, and a circuit through disconnect signal lamp 25 isestablished from battery, through normal contact 4:7 of relay 27, normalcontact 55, alternate contact 59, through the lamp 25 to'ground,lighting the. said lamp. The-trunk operator in response to this signalwithdraws plug 24 from jack 40-, thus opening the circuit throughsupervisory relay SR and the cutoff relay CO, allowing the said relaysto deen'ergize. Upon deenergization of relay SB thecircuit throughsignal lamp 25 is interrupted efiacing the said lamp. Also,upon'de'nergization of relay .SR, the locking circuit forrelay SC isinterrupted at contact M allowinglsaid relay SC to deen- .ergize andretract its armature. The apparatus of trunk circuit B having now beenrestored, and being in an idle condition is available for further use.

Should a called subscriber, after having responded to a call, desire toconverse With one of the operators, by operating his switch hook,the-circuit through the supervisory relay TR will he -opened, allowingthe said relay to retract its armature, thereby openand substitutingtherefor a high resistance path through relay27, thereby againdeenergizing the supervisory relay 10 of cord circuit A and flashing thesupervisory lamp 12. ;flhe operator at cord circuit A observing thissignal, may connect the operators telephone 0 with cord circuit A andconverse with the culled subscriber at substation D. v I

It will be noted that due to the circuit arrangement as heretoforedescribed, that any premature, incidental, momentary energization of thesupervisory relay TR will not affect the signal controlling relay SC,and therefor it will require an ener 'zation of relay TB of someduration to e ect an energization of the signal controllingrelaySC.

What I claim as new and desire to secure by Letters Patent is; 7

1. Ina telephone system, a trunk circuit for connectin calling andcalled substations, compris1ng a trunk supervisory relay adapted to beoperativelyenergized uponrespouse from a called substation whenconnected thereto, a signal controlling relay for said trunk circuitadapted to be energized responsive to a responsive energization of thesupervisory relay,- a signal operated responsive to such energization ofthe signal relay, and means to prevent said signal relay i from beingenergized responsive to an moidental momentary operation of saidsupervisory relay.

. 2. In a telephone system, the combination with a trunk circuit of acord circuit connected to the incoming end thereof, a calledsubscribers.sub-station connected to the outgoing end thereof, a trunksupervisory relay connected to a talking strand of the calledsub-station, adapted to be operatively energized upon response of thecalled subscriber,

- a signal controlling relay for said trunk circuit adapted to beenergizedresponsive to a responsive energi'zation of said supervisoryrelay, atrunk signal controlled'by said signal relay, means forconnecting calling current to said strand, and means to prevent anyenergization of said signal relay responsive to an incidental momentaryoperationof said supervisory relay. I

3. A telephone system including a trunk circuit, a link circuitconnected to theincoming end thereof, a called subscribers lineconnected to the outgoing end thereof, a relay in bridge of saidincoming end, energized by current from said link circuit, a supervisoryrelay for said trunk adapted to be energized upon response of the calledsubscriber, and having normally closed contacts controlling said bridgedrelay, a signal cont-rolling relay, adapted to be energized responsiveto energiza t'ion of said supervisory relay and deenergization ofsaidbridged relay, and means for momentarily holding the armature of saidbridged relay attracted and said contacts open, after an energization ofsaid supervisory relay.

4. In a telephone system, a trunk circuit, a relay in bridge of theincoming end thereof, an energizing circuit for said relay, 9.

supervisory relay for said trunk adapted to' be energized uponresponseof a connected called subscriber, a second relay, switch contacts onsaid supervisory relay adapted upon energization of said supervisoryrelay to interrupt the energizing circuit of the said bridged relay andinclude said second relay in said energizing circuit, means formomentarily holding the armature of said bridged relay attracted afterits energizing circuit is opened, a signal controlling relay, and anenergizing circuit therefor adapted to-be slow relay to deenergize itand substituting said second. relay to be energized, a supervisoryrelay, adapted to be energized upon response of a called subscriber whenconnected to, for controlling said switch contacts, a signal controllingrelay, and an en ergizing circuit therefor, adapted to be closed upondenergization of said slow relay and energization or said second relay.

6. A telephone system comprising an operator controlled link circuit, acalled telephone line and substation connected thereto, a responsesupervisory relay individual to said link circuit, a signal controlrelay for said link circuit adapted to be operatively energized by aresponsive operation ofthe supervisory relay, a locking circuit for saidsignal control relay effective upon its energization, a supervisorysignal for said link circuit operated when said signal control rewherebya premature momentary operation of said response relay does not effectany energization of the signal control relay.

7. A telephone system comprising a-link circuit, a slow relay energizedby current over the answering end of said circuit, a supervisory relayconnected to the calling end of said link circuit and adapted to'beenergized upon response from a connected called substation, a thirdrelay, said supervisory relay being adapted when energized to disconnectsaid slow relay and substitute said third relay to be energized, asignal control relay, and an energizing circuit therefor adapted to beclosed when said slow relay is denergized and said third relayenergized.

Signed by me at Chicago, county of Cook, and State of Illinois, in thepresence of two witnesses.

CHARLES S. WINSTON. Witnesses:

GEORGE E. MUELLER, WM. BERGIELAHN.

